In order to control air pollution, efforts have been made in recent years for developing natural gas motor vehicles and fuel cell motor vehicles which produce clean emissions. These motor vehicles have installed therein a pressure vessel containing fuel natural gas or hydrogen gas to a high pressure.
Among conventionally-known liners for use in such a pressure vessel is one comprising a cylindrical trunk and head plates for sealing openings in both ends of the trunk. The liner is composed of: a first liner component which is made of an aluminum extrudate, has the shape of a cylinder opened at both ends, and forms the trunk; and two second liner components which are made of die-cast aluminum, are generally dome-shaped, and are welded to both ends of the first liner component to form the head plates. A plurality of reinforcing walls are integrally formed on the inner periphery of the first liner component to a radial pattern in cross section. Reinforcing walls are integrally formed on the inner peripheries of the second liner components at positions corresponding to the reinforcing walls of the first liner component (for example, see JP-A No. 9-42595).
For use as a pressure vessel, the pressure vessel liner described in the foregoing publication is provided with: a helical winding fiber reinforced resin layer formed by winding a reinforcing fiber across both the second liner components in the longitudinal direction of the first liner component, and impregnating and fixing the same with an epoxy resin; and a hooped fiber reinforced resin layer formed by winding a reinforcing fiber around the first liner component in the peripheral direction thereof, and impregnating and fixing the same with an epoxy resin.
By the way, motor vehicles require pressure vessels of higher capacities for the sake of extended cruising distances. In the pressure vessel using the pressure vessel liner described in the foregoing publication, a higher capacity can be achieved by increasing the diameter of the trunk and increasing the length thereof. Since motor vehicles have limitations in vehicle width, and thus also have limitations in increasing the length of the trunk, the higher capacity of the pressure vessel must be achieved by increasing the diameter of the trunk. When the diameter of the trunk is increased, however, it is impossible to make effective use of free spaces existing in motor vehicles. This gives rise to the problem of causing wasted space in the car-mounted state and deteriorating the comfort of the cabins. There is also the problem that increasing the diameter of the trunk requires a greater vehicle height and thus precludes use with motor vehicles of smaller heights such as a sedan.
An object of the present invention is to overcome the forgoing problems and provide a pressure vessel which can be installed with no wasted space and can achieve an increase in capacity.